Hydro-balanced pump



June 14, ;1960 c. v. ZIEG ETAL 2,940,399

HYDRO-BALANCED PUMP Filed April 25, 1958 2 Sheets-Sheet 1 U Q/ 22 m g 26 2-11 68 12 1 g z 12 l INVENTORS C11; 0rd, V. Z 1'6 g R0 ertD. Lambert ATTORNEY ner rotor or idler gear bearing.

the disc.

United States Pater 1ft)" HYDRO-BALANCED PUMP Clifford V. Zieg and Robert D. Lambert, Fort Wayne,

Ind., assignors to Symington-Wayne Corporation, Salisbury, Md., a corporation of Maryland Filed Apr. 25, 1958, Ser. No. 731,054

11 Claims. (Cl. 103-126) This invention relates to a rotary gear pump of the type which includes an inner rotor eccentn'cally meshed Within an outer rotor, and more particularly relates to a pump of this type in which means are provided for balancing the pressure forces acting on the rotors.

In rotary gear pumps of the type having an inner rotor eccentrically meshed Within an outer rotor, the outer rotor generally incorporates a cylindrical disc having gear teeth extending longitudinally from its outer periphery. During operation, a differential pressure is created across portions of the disc lying between the inlet and outlet ports. This differential pressure reacts unevenly upon the front face of the disc causing bending stresses to be set up in the rotor disc and shaft and urging the disc against the casing in areas exposed to relatively higher discharge pressures.

Other problems encountered with this type of pump are the transmission of excessively high fluid-squeezing forces to the rotor teeth when they are intermeshed and the difliculty of insuring adequate lubrication for the in- Various attempts have been made to solve each of these problems individually, but heretofore, no simple and economical unitary scheme for simultaneously solving or eliminating each or all of the aforementioned problems has been either proposed or put into practice.

An object of this invention is to provide a simple and economical unitary scheme for balancing the pressure forces reacting upon the rotors and for preventing the creation of excessive fluid-squeezing forces betweenthe intermeshing teeth of a rotary gear pump incorporating eccentn'cally meshed inner and outer rotors.

Another object of this invention is to provide a unitary scheme of the aforementioned type which also lubricates the bearings. v

In accordance with this invention, the pressures reacting upon both faces of the outer rotor disc are equal- I ized by providing balanced sets of pockets of fluid under pressure reacting against the front and back faces of the disc. vAxially aligned pockets of these sets are connected by equalizing passageways extending through the disc.

One of these pockets lying adjacent the front of the disc is created by recessing the front face of the hub of the inner rotor. This provides a centrally disposed cylindrical pocket surrounded by a pressure-sealing rim which engages in sliding contact with the front face of Outer pressure pockets or areas, which are constituted by the portions of the disc exposed to suction and discharge pressure, surround this rim on two sides.

One pressure pocket in contact with the back of the disc is provided by recessing a portion of the casing disposed adjacent the back face of the disc in an annular area disposed about the hub of the disc. The outside diameter of this annular recess is substantially equal to that of the cylindrical recess in the hub of the inner rotor.

Outer pressure areas or pockets in contact with the back of the disc are provided by recessing portions of ice the casing substantially axially aligned and substantially equal in area with the areas at the front of the disc which are exposed to the suction and discharge pressures. The portions of the casing lying between these recessed pressure areas are constructed and arranged to engage the back of the disc in sliding contact to provide pressuresealing barriers disposed adjacent the back of the disc which maintains a pressure differential between the fluids in the central and outer recesses. Any slight leakage which occurs between these pressure-sealing barriers and the face of the disc does not prevent this pressure differential from being maintained. The sealing area of these barriers is made substantially equal to the area of the annular rim of the inner rotor which contacts the face of the disc to permit the rim and barriers to maintain similar differential pressures. The rim is, therefore, also referred to as a pressure-sealing barrier.

Equalizing passageways are bored axially through the.

disc, for example, adjacent the tips of the outer rotor teeth and on their center lines. Another passageway connects the recessed-annular area of the casing with a portion of the pump cavity communicating with the suction port. Still another equalizing passageway is provided extending through the inner rotor hub and connecting the pressure pockets adjacent the central portions of both sides of the disc. These passageways in conjunction with the aforementioned recesses and pressuresealing barriers maintain balanced films of fluid flowing on both sides of the disc from the outer pocket disposed adjacent the discharge port to the inner pockets disposed adjacent the central portions of the disc. This slight flow of fluid is ultimately conducted to the suction side of the pump by connecting the central pocket behind the hub of the disc to the suction side of the "nular pocket in the casing with the outer pocket in the casing on the suction side of the pump. A slight amount of fluid also flows in a film from the central pockets to the outer areas across the pressure-sealing barriers.

A convenient supply of lubricating fluid for the outer rotor bearing is provided by disposing one of its ends in communication with the central pocket behind the hub of the disc and connecting the other of its ends with the suction side of the pump.

A convenient supply of lubricating fluid for the inner rotor or idler bearing is provided by boring a passageway extending from the high pressure side of the pump through the casing and idler pin. This passageway breaks through the surface of the idler pin approximately at the center of the bearing. The face of the inner rotor hub remote from the disc is recessed in a manner similar to its other face to provide a similar rim and pressure pocket. An equalizing passageway extends axially through the hub of the inner rotor to interconnect the pressure pockets in both of its faces. The fluid flowing through the idler pin, therefore, divides substantially equally and flows in both axial directions through the bearing and into the equalizing passageway in the hub of the disc, either directly or indirectly through the equalizing passageway in the hub of the inner rotor.

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with 'the accompanying drawing wherein similar reference I along the line 22 and looking in the direction of the arrows;

Fig. 3 is a view in elevation of a portion of the embodiment shown in Fig. 1;

72 and 90 to the portion of faces 62 and 64 exposed to suction pressure.

A convenient supply of lubricating fluid for bearing means 100, within which outer rotor shaft 32 is rotatably mounted, is provided by disposing one end 102 of bearing means 100 in communication with pocket 76 behind disc hub 34 and connecting the other end 104 of bearing means 100 with the suction side of the pump by disposing the entrance to passageway 98 at end 104 of heating means 100. A slight leakage of fluid to lubricate bearing 100, therefore, flows along shaft 32 into a cavity 106 to which passageway 98 connects. The outer end of cavity 106 is. sealed, for example, by a conventional set of spring-biased mutually contacting sealing discs 107 and 109.

A convenient supply of lubricating fluid for the rotating bearing surface of inner rotor 12 is provided by boring a passageway 108 extending through casing head 44 from the high or discharge pressure side of cavity 16, and connecting it to a passageway 110 which extends through idler pin 74. Passageway 110 breaks through the bearing surface 1120f idler pin 74 approximately at the longitudinal center of bearing surface 112.

Face 114 of inner rotor hub 70 remote from disc 30 is recessed in a manner similar to face 68 to provide a central pocket 116 and an annnular rim 118 respectively similar to pocket 66 and rim 72. An equalizing passageway 120 extends axially through hub 70 of innner rotor 12 to interconnect pressure pockets 116 and 66. The fluid flowing along the surface 112 of idler pin 74, therefore, divides substantially equally and fiows in both axial directions along bearing surface 112 and into equalizing passageway 96 in the hub 34 of disc 30 either directly or indirectly through pocket 116 and equalizing passageway 120.

Passageway 122 extends through casing 18 at a 180 relationship to passageway 103 to permit a single casing structure to be used for pumps operating in either direction of rotation. In the directionof rotation herein indicated, passageway 122 is sealed by a plug 124.

' Operation In Fig. 5 are shown various graphs illustrating the forces reacting upon portions of faces 62 and 64 of disc 30 which are disposed, for example, along line 40 extending through the center of disc 30. Corresponding portions of outer rotor 14 are also shown to correlate the illustrated forces with the parts of the structure upon which they act. These parts are, for example, outer rotor 14 including teeth 26, equalizing passageways 92 extending axially through disc 30, and passageway 96 extending through hub 34 of disc 30, hearing 100, and central annular recess 76 adjacent hub 34.

Continuous lines 126, 128, 130 and 132, disposed above rotor 14, represent the pressure forces reacting along line 40 on the front face 62 of disc 30. The pressure force accordingly drops, for example, from 100 p.s.i. adjacent discharge port 22 and represented by line 126 to 50 p.s.i., for example, across sealing barrier or annular rim 72 incorporated in the face of idler gear 12 as represented by line 128. This pressure remains constant along line 130 across pocket 66 and then drops to 0 p.s.i. or suction pressure along line 132 across the portion of pressure-sealing barrier or annular rim 72 adjacent suction port 20.

Continuous lines 134, 136, 138 and 140 represent the pressure forces reacting on the back face 64 of disc 30 along line 40. Line 134 represents a discharge pressure of, for example, 100 p.s.i. The pressure drops to 50 psi. along line 136 across pressure-sealing barrier 88. The pressure remains constant slightly lower than 50 p.s.i., for example, approximately at p.s.i. through pocket 76 as represented by line 138, by virtue of the connection of pocket 76 through bearing 100 and passageway 98 to the suction sde of the pump at pressure pocket 82. A drop, for example, from 45 p.s.i. to atmospheric or suction pressure occurs along line 140 as the fluid passes across pressure-sealing barrier 90 into suction pressure pocket 82. A comparison of aligned portions of continuous lines 126, 128, 130, and 132 with corresponding continuous lines 134, 136, 138 and 140 indicate that the pressure forces reacting on faces 62 and 64 of disc 30 substantially balance each other.

What is claimed is:

1. A rotary pump comprising a casing including a cylindrical cavity having an inlet and outlet port extending through said casing into said cavity, an outer rotor including a cylindrical disc mounted upon a shaft, a bearing means mounted upon said casing for rotatably supporting saidshaft, outer rotor teeth disposed about the periphery of said disc and extending longitudinally therefrom, an inner rotor having teeth, said inner rotor being rotatably mounted within said cavity in eccentric meshing engagement within said outer rotor to provide spaces between said teeth of said rotors of varying size about the periphery of said inner rotor, the number of teeth upon'said inner rotor being less than the number of teeth upon said outer rotor, the face of said inner rotor adjacent the front face of said disc being recessed to provide a central pocket and an annular rim of predetermined area which engages said front face of said disc in pressure-sealing contact therewith, a portion of said casing adjacent the back of said disc being recessed in a central annular area disposed around said shaft and in outer areas approximately in axial alignment with and approximately equivalent in eifective pressure area with areas at the front of said disc exposed to suction and discharge pressures to provide pressure forces reacting behind said disc which substantially balance the pressure forces reacting upon the front of said disc, portions of said casing lying between said outer areas being constructed and arranged to engage the back of said disc in sliding contact to provide pressure-sealing barriers which maintain a differential between said central and said outer areas, 'said pressure-sealing barriers being constructed and arranged to provide sealing effects equivalent to said rim, equalizing ports extending axially through said disc from the front to the back of said disc adjacent said rotor teeth to provide in conjunction with the pressure-sealing barriers substantially balanced forces reacting upon the front and back of said disc, and channel means connnecting said central recessed area of said casing with a lower differential pressure portion of said casing to promote a fiow of fluid through said equalizing ports.

2. A rotary pump as set forth in claim 1 wherein one end of said bearing means is connected to said annular area of said casing, and conduit means connects the other end of said bearing means to a portion of said casing adjacent said suction port to promote a lubricating flow of fluid from said annular recess through said bearing.

3. A rotary pump as set forth in claim 1 wherein one of said equalizing ports is provided adjacent the tip of each of said outer rotor teeth.

4. A rotary pump as set forth in claim 3 wherein one of said equalizing ports is disposed upon the center line of said outer rotor teeth and contiguous to their tips to relieve excess pressures created when said inner and outer rotor teeth mesh with each other as well as equalizing the pressures between the front and back faces of said disc.

5. A rotary pump as set forth in claim 1 wherein an outer recessed area in said casing is provided adjacent said discharge port and adjacent said suction port, and a channel is provided between said central annular recess in said casing and said outer recessed area in said casing disposed adjacent said suction port to promote flow of fluid from said central annular recess to said suction port.

6. A rotary pump as set forth in claim 1 wherein said pressure-sealing barriers are approximately axially aligned of inner rotor,

V "7. A rotarygpump, as set forth in claim 6 whereinthe outer peripheries of, said outer areas are arcs of-a circle of constant radi'us. having-a: common center with the cent r said yl n rical vity Y 8; A rotary pump as set forth in claimd" a passageway extends through the hubof; said disc adjacent said shaft to promote a flow of fluid into said recess in, the face of said. inner rotor'an'd forbalancing theforces' reacting'uponsaid'hub. V i H V 9. A rotary pump as set forth in claim 8 whereinv the faceofi saidinner rotor remote'frqmsaid. disc-is receSsBd to providea second annularrim surrounding iaficentral pressure area; and a second passageway" extends axially through the hub of said inner, rotor to'conneetsaid re-' cesses in' both of" 'said' faces of said inner rotor forl ralancing the forces reacting.upon both faces. of said inner rotor; V

10. A rotary pump as set forth in claim 9whereina include a passageway extending from a portion of said aamaas cavity exposed 1 to, discharge pressure through said pin andbreakingthrough the cylindrical surface of said; pin

' tending fromthe Qther'end ofs aid bearingfmea-ns' to a pin is'mounted upon a side of said casing opposite from portion" of? said'-' casing-exposed to. suction pressure to promote a flow of fluid between said inner rotor and said bearing surface of said pin land thenthrou-ghsaid bear ing' means to lubricate said bearing surface said bearing meansl ass well as balancing the forces reacting upon said rotors.

References Cite d' in the fileof this patent UNITEDSTATES PATENTS, 2,1;24;14o' Foster r a1. Y 1 Iu1y'14; 1932; 2,516,589 7 Pond etall; limb 25,1950 Parsons Sept. 1, 1 953 

